The present invention relates to a roulette-type disc changer, and particularly to a roulette-type disc changer which can sense a disc number using a laser beam from an optical pickup, without using an extra photo sensor.
Along with the advent of the compact disc (CD), various types of CD players have been introduced. While some such players accommodate (as for reproducing) a single disc, a CD player system in which a plurality of discs can be accommodated has been developed recently, which is called a roulette-type disc changer. One example of a conventional roulette-type disc changer is shown in FIGS. 1 and 2, where FIG. 1 is a plan view thereof and FIG. 2 is a cross-sectional view which is cut along line II--II of FIG. 1.
Referring to FIGS. 1, 2 and 3, the conventional roulette-type disc changer 10 comprises a round tray 11 having a predetermined thickness and width, and a round roulette 12 which is installed on a rotary shaft 16 located at the center of tray 11, to rotate the roulette 12 thereon. A plurality of L-shaped holder chucks 11a for supporting a plurality of discs 13 are provided around the circumference of tray 11 at a predetermined interval from each other. Fixing members 13s for preventing disc separation from the roulette are installed in each chuck 11a, so as to be positioned over the center of each disc 13. Photo sensors 15 are installed in a circular pattern on the upper surface of tray 11, for sensing disc-number sensing interrupters 14a, 14b and 14c and a roulette-stop sensing interrupter 14d which are arranged in a corresponding circular pattern on the lower surface of roulette 12, as shown in FIG. 3.
In the operation of the above conventional roulette-type disk changer, when roulette 12 loaded on tray 11 rotates, the disc-number sensing interrupters 14a, 14b and 14c and roulette-stop sensing interrupter 14d pass above photo sensors 15 installed between tray 11 and roulette 12. Accordingly, each interrupter intercepts the light of photo sensors 15 so that the disc number can be sensed by the different number of light interceptions, which is in accordance with the number of interrupters 14a, 14b or 14c. The stop position of roulette 12 is detected by roulette-stop sensing interrupter 14d.
However, the above-described system for sensing disc number and roulette stop position requires an additional set of photo sensors and interrupters for each disc. Therefore, the manufacturing cost of a CD player is increased accordingly and the interrupter formation is troublesome.